Memorial Day honors the sacrifice of servicemen and women who gave their lives to defend our country and way of life. But Memorial Day weekend also marks the traditional start of the summer driving season, during which many of us take to the roads for travel and vacations. This Memorial Day, it's important that we reflect on both aspects of the holiday -- and understand the connection between the two.

America's addiction to oil is a threat to our national security, as well as our economy and our environment. This connection is important enough that the Sierra Club and the American Security Project have recognized the shared need to come together to talk about it:

TRANSPORTATION: The U.S. uses nearly 400 million gallons of oil every day moving people in automobiles, goods on freight truck, air travel, rail and transit. Of all the oil used in the United States, 70% is consumed by transportation. Cars and light trucks use nine million barrels of oil per day.

NATIONAL SECURITY: Of the imported petroleum Americans consume, 68 percent is supplied by countries at "high risk" or "very high risk" for instability. Oil dependence gives leverage and money to potential adversaries, and risking embroiling the U.S. state in endless conflicts abroad to secure access to oil.

ECONOMIC SECURITY: Americans send over $1 billion abroad every day to pay for oil, resulting in lost jobs and increasing dollars in the hands of foreigners who we increasingly rely upon to finance our deficits. The U.S. borrows money from the Chinese to buy oil from the Saudis, causing greater national debt and dependence on the goodwill of others to allow its economy to function.

ENVIRONMENTAL IMPACT: The BP oil disaster in the Gulf of Mexico is an example of what could happen again if we increase off-shore drilling. In the United States, burning fossil fuels for electricity and transportation is the largest contributor to global warming pollution. Transportation is responsible for approximately one-third of all U.S. carbon dioxide emissions.

America can do better we can end our oil addiction. Meeting this challenge will not be easy, but nor will it require tremendous sacrifices. We can address our national security and climate change concerns with a series of smart and interconnected policy options that will gradually transition the country to a post-oil economy.

SOLUTIONS:

Tightening fuel economy standards for all vehicles;

Promoting the development and deployment of electric vehicles of all types;

Investing in rail for freight and also passengers;

Creating livable communities where transit, walking and biking are real and oil-free choices;

and exploring biofuel and hydrogen fuel as alternatives to oil.

This Memorial Day, we should honor the brave men and women who fought for this country, and at the same time we should examine what we can do to mitigate the threat to American security of oil dependence. It's time to call on President Obama to create a solid plan for ending our country's dependence on oil.